A technology that measures a Brillouin scattered light spectrum that are generated in accordance with a pumping light input that is obtained from an optical fiber placed in the vicinity of a measurement object and measures the temperature and strain of the optical fiber as a physical change in the measurement object on the basis of the parameters of the measured Brillouin spectral is known (See Non-Patent Document 1).
However, in the technology mentioned in Non-Patent Document 1, when an optical fiber of the same type is applied in a measurement area and in another area (a non-measurement area), the respective Brillouin spectra overlap and accurate Brillouin spectrum measurement of the measurement area is not possible. There is also the problem that it is hard to know of the position of the measurement object.
In response to this problem, for example, Patent Document 1 mentions a technology that discriminates a measurement area and non-measurement area by connecting a wavelength 1.3 μm optical fiber to a wavelength 1.55 μm optical fiber while pasting the optical fiber with a wavelength of 1.55 μm onto the measurement area and measuring the spectrum of the Brillouin scattered light output by these optical fibers of two types.
Patent Document 1: Japanese Patent Application Laid-Open No. H11-287670
Non-Patent Document 1: Nikles, et al., ‘Brillouin Gain Spectrum Characterization in Single-Mode Optical Fibers’, Journal of Lightwave Technology, October 1997, vol. 15, no. 10, pages 1842 to 1851